The invention discloses a DTS-based design method of a detection system for detecting the integrity of a cast-in-place pile. According to the DTS-based design method, linear optical fibers are planted into a pile body with the cross radius of the pile of R and are distributed along the central line; the planted optical fibers are used as an inner heat source and are heated; an influence radius of heat conduction is r0, Ts is a rock and soil medium temperature, and temperatures of the pile body and an outer surface are equal to the rock and soil medium temperature under an initial condition; a critical radius r0 can be determined through distributing a plurality of optical fiber sensors at different distance parts in the pile body along the central line, and a heat conductivity coefficient k can be determined through a DRPL-II heat conductivity coefficient tester; optical fiber heating power q can be calculated through an equation according to known DTS instrument precision delta. According to the DTS-based design method disclosed by the invention, defect detection of the large-diameter concrete cast-in-place pile is taken as a research object and the proper quantity of the planted optical fibers is determined; the heating radiation critical radius r0 and the heating power q are calculated, so that evidences are provided for design indexes in a DTS detection process; rapid and complete detection can be realized, and the design method has prompting meanings on standard DTS pipe defect detection.